Moving_Boundary

Syntax

Bc Lumped_Flux For Mass_Balance ([{of} SpeciesName] | [{in} MaterialPhaseName] | [{ls} {a | b | c}]) {@ | at | for | on | over} Mesh Extent Name ([Touching TouchingMeshExtent] | [Opposing OpposingMeshExtent]) = Moving_Boundary [Toggle = toggle]

Summary

No penetration moving boundary condition, valid for Lagrangian mesh motion in non-relative flux form or relative flux form.

Description

Applies the following boundary flux

\int q \mathbf{\hat{u}} \cdot \mathbf{n} dS,

where \hat{u} is the mesh velocity and where the integrated scalar q depends on the equation. If we consider the gas phase porous_enthalpy equation with a transported enthalpy = porous, then q = \phi \rho_g h_g. Similarly, for the gas phase mass_balance equation, q = \phi \rho_g is the bulk mass density.

If we consider the gas phase mass_balance equation, with a gas phase porous velocity relative to the moving solid phase, then physically this boundary condition is derived from applying a no flux condition at moving boundary i.e.,

\mathbf{u}_g \cdot \mathbf{n} = \phi \mathbf{\hat{u}} \cdot \mathbf{n}.

In the Lagrangian setting, this flux is required to impose a no flux condition at the moving boundary with both the non-relative form (default) and relative form of the advection term. When using the relative form, typically a do-nothing condition would be sufficient to impose no flux; however, to simplify general ALE mesh motion for porous flow equations (i.e., mass balance and porous enthalpy) we automatically provide the mesh motion flux on boundaries for blocks that have mesh motion. Consequently, to impose a zero flux, this term is needed for cancellation.

The following options are present in most boundary conditions/sources. The meaning of each option is as follows:

Toggle

If given, specifies which toggle block controls whether this BC is active or not.

Parameter

Value

Default

{of}

{of | species | subindex}

–

SpeciesName

string

–

{in}

{in | material_phase}

–

MaterialPhaseName

string

–

{ls}

{levelset_phase | ls}

–

Mesh Extent Name

string

–

TouchingMeshExtent

string

–

OpposingMeshExtent

string

–

toggle

“string”

–